1. Field of the Invention
The present invention relates to a liquid material supply system and method for supplying a liquid material employed in semiconductor manufacturing and, more particularly, to an apparatus that employs gas pressure to supply a liquid material. Corrosive and toxic liquids are often used in semiconductor manufacturing and can be advantageously propelled by a source of inert gas while avoiding contact with traditional pumping hardware.
2. Description of Related Art
In the case where a liquid material is supplied to a use point while its flow rate is controlled, a gas pressure driven system, where pressure surges or ripples are few and the gas can be easily pressurized, is often used as a propelling system for the liquid material. In this gas pressurization system, an inert gas such as helium is injected into a material tank containing the liquid material so that the liquid material is forced into a discharge pipe.
In the present case, when the inert gas is being injected into the material tank, the inert gas can become dissolved in the liquid material up to its saturation amount according to Henry's law. When a large difference of elevation or pressure loss exists in the liquid material discharge pipe connected to the material tank, the pressure of the liquid material discharged into the liquid material discharge pipe decreases and the gas dissolved in the liquid material can be released so that the flow control becomes unstable.
Thus, in a conventional liquid material supply apparatus of this type, a gas trap is provided for capturing and removing the dissolved gas as much as possible. However, even when such a gas trap is provided as described above, such dissolved gas still may persist in higher than acceptable amounts.
Meanwhile, the temperature characteristic of a dissolved gas volume with respect to a liquid indicates an eigenvalue in accordance with the types of the liquid and the gas. For example, in the case where the dissolution temperature characteristic of the volume of a dissolved gas with respect to a liquid is negative, that is, in the case where the dissolved gas volume decreases with increasing temperature, release of the dissolved gas (degassing) can be facilitated by heating the liquid material. Conversely, in the case where the dissolution temperature characteristic of a dissolved gas volume with respect to a liquid is positive, that is, in the case where a dissolved gas volume increases with increasing temperature, release of the dissolved gas can be facilitated by cooling the liquid material.
The present invention has been made while attention is directed to the above described matters, and it is an object of the present invention to provide a liquid material supply system and method in which the dissolved gas in the liquid material can be reliably removed.